Ridged waveguide microwave switch



April 9, 1957 c. E. VOGELEY, JR ET AL 2,788,494

RIDGED WAVEGUIDE MICROWAVE SWITCH Filed Dec. 5, 1951 2 Sheets-5heet 1Fig.1.

WITNESSES: INVENTORS C|ydeE.V0geley Jr. 6%77/ and Thaddeus Absio l.

- ATTORNEY April 9, .1957 c. E. VOGELEY, JR., ET AL 2,738,494

RIDGED WAVEGUIDE MICROWAVE SWITCH Filed Dec. 5, 1951 2 Sheets-Sheet 2WITNESSES: lNVENTORS,

. 4 7 Clyde E.Voge|ey 777/ 0nd Thaddeus A.O

ATTORNEY United States RIDGED WAVEGUIDE MICROWAVE SWTTCH Clyde E.Vogeley, Jr., and Thaddeus A. Osial, Pittsburgh, Pa., assignors toWestinghouse Electric Qorporation, East Pittsburgh, Pa., a corporationof Pennsylvania Application December S, 1951, Serial No. 259,914

9 Claims. (Cl. 3337) Our invention relates to conductors forelectromagnetic oscillations, and more particularly, to apparatus forcontrolling the flow of oscillations in ridged waveguides.

In accordance with the prior art of which we are aware, microwave switchdevices have been built which employ such types of apparatus as swinginggates, rotating discs with apertures conforming to the waveguide crosssection cut therein, or plunger-s moving up and down into the guide.These devices have many disadvantages, such as the requirement of spaceconsuming auxiliary gear which is often quite cumbersome. Also thesedevices are not readily employable with a ridged Waveguide in view ofits complex geometry.

In situations where it is desirable to provide a Y-section having threebranches, it is usually desirable that two of the branches be isolatedfrom each other. f-sections and standard waveguides have been built inwhich a septum comprising a thin sheet of metal is placed at thejunction of the two branches which are to be isolated from each other.However, this does not isolate the branches to the degree which isusually desired.

It is accordingly an object of our invention to provide an improvedmicrowave switching apparatus.

Another object of our invention is to provide an improved microwaveY-section.

Still another object of our invention is to provide a new and usefulapparatus for controlling the flow of electromagnetic oscillations.

The ridged waveguide which is commonly employed in the art comprises ahollow conductor having a substantially rectangular cross section.Extending into the hollow conductor is a re-entrant portion also ofelectrically conducting material, this re-entrant portion beinggenerally referred to as a ridge. The re-entrant portion extends alongthe length of the hollow conductor and is located approximately half waybetween the two sides of the hollow conductor. The re-entrant portionextends up from the bottom a distance which is roughly equal to half theheight of the waveguide, the exact height depending on the use to whichthe waveguide is to be put. The ridged waveguide has the advantage overthe standard rectangular waveguide of having a lower cut-otf frequencythan a standard waveguide having the same overall cross sectionaldimensions.

In accordance with our invention, we provide a section of waveguidehaving therein over a portion of its length a re-entrant portionextending thereinto, thereby forming a ridged waveguide over a portionof the length of the waveguide and a standard waveguide over theremainder of the length of the waveguide.

Since the portion of the hollow conductor which contains the ridge has alower cut-off frequency than the portion of the hollow conductor whichdoes not contain the ridge, oscillations may be caused to flow freelythrough the region where the ridge is located, while being completelyprevented from traversing that portion of the chamber where the ridge isnot located. Thus, by'connecting two conductors to the chamber atdiffercut points along the length of the chamber and by properadjustment of the location of the ridge, oscillations may be eithercaused to flow from one conductor to another or alternatively, to beprevented from flowing from the one to the other.

The novel features which we consider characteristic of our invention areset forth with more particularity in the appended claims. The invention,however, with respect to both the organization and the operationthereof, together with other objects and advantages may be bestunderstood from the following description of specific embodiment whenread in connection with the accompanying drawings, in which:

Figure 1 is a showing in section of a microwave switch built inaccordance with one embodiment of our invention,

Fig. 2 is a showing in section of the apparatus shown in Fig. 1, takenalong the line lIII of Fig. 1,

Fig. 3 is a showing in section of a Y-section built in accordance withanother embodiment of our invention,

Fig. 4 is a showing in section of the apparatus shown in Fig. 3, takenalong the line IVIV of Fig. 3.

In accordance with our invention, we provide an inner cylinder 6 and anouter cylinder 8 of electrically conducting material. The outer cylinder8 is hollow and has an internal diameter substantially greater than theoutside diameter of the inner cylinder 6. The inner cylinder 6 islocated inside the outer cylinder 8 and is oriented coaxially therewithso as to form a cylindrically shaped hollow region between the inner andouter conductors 6 and 8. At one end of the inner and outer conductors 6and 8 is placed a top plate 10 which fills the cylindrically shapedregion between the inner and outer cylinders at that end. At the otherend of the cylinders 6 and 8 from that at which the top plate 10 islocated, there is a bottom plate 12. The bottom plate 12 in conjunctionwith the inner cylinder 6, the outer cylinder 8, and the top plate 10forms a cylindrical shaped chamber or cavity of rectangular crosssection. The bottom plate 12 includes a rectangularly shaped projection16 which extends into the chamber 14 so as to form, in conjunction withthe walls of that chamber, a ridged waveguide over a portion of thelength of the chamber. In a preferred embodiment of our invention, theprojection 16 is adjustably mounted so that it may be rotated about theinner cylinder 6 by applying a torqueto a handle 18 to which theprojection 16 is connected. Thus the projection may be moved to thedesired position along the length of the chamber 14 by rotating it aboutthe inner cylinder 6.

In the embodiment shown in Figs. 1 and 2, a first branch ridgedwaveguide 20 is coupled to the chamber 14 at a first point along thelength of the chamber 14. A second branch ridged waveguide 22 is coupledto the chamber 14 at a point geometrical degrees around the chamher 114from the point Where said first branch wave guide 25} is connected. Athird branch ridged Waveguide 24 is coupled to the chamber 14 at a pointequally distant from the point where the first branch 2t! is coupled tothe chamber 14 and the point where the second branch 22 is coupled tothe chamber 14.

In the preferred embodiment of our invention the projection 16, whichextends into the chamber has a length in the direction in which thechamber 14 extends such that it extends around the chamber a distancegreater than a quarter, but less than a half of the length chamber 14.

When the projection 16 is located as indicated in Fig. 1, namely so thatit extends from the region of the first branch guide 29 to the region ofthe third branch guide 24, but does not extend into the region of thesecond branch guide 22, there is efiectively provided, a ridged of the lwaveguide between the first branch guide 2% and the third branch guide24. However, a standard Waveguide is provided between the first branchguide it) and the second branch guide 22 and between the second branchguide 22 and'the third branch guide 24.

Whenthe frequency of the oscillations employed in the waveguides is suchthat the section of the chamber which represents efiectively a standardwaveguide is below the cut-ofi dimensions corresponding to thatfrequency while the dimensions of the section of the chamber containingthe projection 16 are such to produce a ridged waveguide,- the cut olfdimensions of which are not below that corresponding to the frequency tobe employed, the oscillations will be allowed: to pass from the firstbranch ridged guide 29 to the third branch guide 2 but not from thefirst branch. waveguide 23th to the second branch waveguide 22.

We have thus taken advantage of the previously explained principlethatwith the same overall cross sectional dimension the cut-offdimension for a ridged waveguide is lowerthan the cut-off dimension ot astandard waveguide. By proper adjustment of the location of theprojection 16, the first branch maybe coupled to the third branch oralternatively the second branch be coupled to the third branch. Also, itis understood that by increasing the length of the projection 16 it ispossible tobuild the apparatus so that the first branch could be coupledto the second branch as well as the third branch or instead of the thirdbranch;

In accordance with another embodiment of our inventionas shown in Figs.3 and 4, a Y-section may be constructed by properly choosing the lengthof the ridge member-16 and thelocation of thebranch waveguide 2Q, 22,,24. In accordance with this emobdiment of our invention the secondbranch 22 and the third branch 24 are coupled to the chamber 14 atpoints equally distant from thepoint' where the first branchwaveguide 2%is connected to. thechamber 14. In this embodiment of our invention, thelength of theridge member 16 and its location are chosen so that itextends from the region of the second branch waveguide 22 past the firstbranch waveuide 26' to the region of the third branch waveguide 24,while causing a discontinuity to'exist in the ridge Waveguide betweenthe second branch 22' and the third branch 24 on the side away from thefirst branch 2d. Therefore, oscillations entering the third branch 24have topass the first branch 2% before reaching the second branch 22.Likewise, oscillations entering the second branch 22 have to pass thefirst branch 24 before reaching' the third branch 24. Thus byproperlychoosing the a length ofthe ridge and byproperly adjusting. thelocation of the ridge, most of the oscillations coming in the secndbranch 22'may'be caused to pass out the-first branch while only a smallpercent pass out the-third branch 24.

In accordance with another embodiment of our invention the ridge member16 may be tapered at the end thereof soas to form a tapered transitionbetween the region capable of. supporting oscillations and the regionwhich is beyond cutoff.

Although we have shown and described specific embodiments of ourinvention, we are aware that other modifications-thereof are possible.Our invention, therefore, is not to be restricted except insofar as isnecessitated by the prior art and the spirit of the invention.

We claim as, our invention:

1. A microwave switch for a given frequency, comprising. an innercylindrical conductor and an outer cylindrical conductor, said innercylindrical conductor having' a diameter substantially less than theinside diameter of outer cylindrical conduct-or, said inner conductorbeing adapted to be" inserted inside said outer conductor so as to forma toroidal cavity between said inner and said outer conductors, a bottomplate filling the region between saidinner and said outer'oonductors atone end of said toroidal cavity and a top plate filling the regionbetween said inner and said outer conductors at the opposite end of saidtoroidal cavity from said bottom plate, said bottom plate including are-entrant portion which extends into said cavity so as to form, inconjunction with the walls of said cavity, a ridged waveguide over afirst part only of the length around the said cavity, said ridgedwaveguide having a cutoff frequency below said given frequency, a secondpart of the length around said cavity comprising a non-ridged waveguide,whereby electromagnetic oscillations below said cutoff frequency. ofsaid ridged waveguide are substantailly prevented from being transmittedthrough said non-ridged waveguide, a plurality of connections forcoupling conductors for electromagnetic oscillations to said cavity,said first part of the length being at least as great as the minimumpart of said length around said cavity which separates two of saidcoupling conductors.

2. Apparatus as described in claim 1, characterized in that the locationof said re-entrant portion is adjustable with respect to the position ofsaid connections.

3. A microwave switch for a given frequency, comprising a toroidalchamber of substantially rectangular cross section having wallsofelectrically conducting material, a re-entrant portion extending intosaid chamber so as to form, in conjunction with the walls ofsaidchamber, a ridged Waveguide over afirst part of the length of saidchamber, said ridgedwaveguide having a cutoff frequency below said givenfrequency, said reentrant portion being discontinuous over a second partof the length around said toroidal chamber so asto form a non-ridgedwaveguide, whereby electromagnetic o'scillations below said cutofifrequency of said ridged waveguide are substantially prevented frombeing transmitted through said non-ridged waveguide and a plurality ofhollow wave-guides for conveying electromagnetic oscilla tions to saidchamber.

4. Apparatus as described in claim 3', characterized in that thelocation of said re-entrant portion is variable around the length ofsaid cavity with respect to the points where said connections arecoupled to said wave-guide.

5. A microwave switch for a given frequency, comprising a rectangularwaveguide extending in a circular direction, said waveguide having atop; a bottom and two sides, one of said sides being on the inside ofthe curve of said waveguide and one of said sides being on the outsideof the curve of said waveguide, a re-entrant portion extending into saidrectangular waveguide over a first portion of its length so as to form,in' conjunction with the walls of said rectangular waveguide over aportion of its length, a ridged waveguide, said ridged waveguide havinga cutoff frequency below said given frequency, said re-entrant portionbeing discontinuous over a second part of the length of said waveguideso as to form a non-ridged waveguide, whereby electromagneticoscillations below said cutoff frequency of said ridged waveguide aresubstantially prevented from being transmitted through said non-ridgedwaveguide and a plurality of conductors for electromagnetic oscillationscoupled to said wave-guide.

6. Apparatus as claimed in claim 5, characterized in that the locationof said re-entrant portion is adjustable with respect to the pointswhere said conductors are coupled to said waveguide.

7. Apparatus as described in claim 5, chara'ctriied in that saidplurality of conductors comprise'a first conductor connected to saidwave-guide at onejp'oint al'on'g' its length, a second conductorconnected tosaid' wave guide at a point 180 geometrical degrees fromsaid first conductor and a third conductor located. at a, pointgeometrical degrees from said first conductor and said second conductor;

8. In combination, a hollow chamber having Walls of electricallyconducting material; said chamberextending in a circle so as to formsclosed loop and having a' substantially rectangular cross section, acircular projection of rectangular cross section extending through awall of said chamber, said projection being of electrically conductingmaterial, a first conductor for electromagnetic oscillations connectedat a first point along the length of said chamber, a second conductorfor electromagnetic oscillations connected to said chamber at a secondpoint along the length of said chamber, said projection extending aroundthe length of said chamber a distance less than the distance around saidcircle but extending a distance greater than the distance between thepoint where said first conductor is connected to said chamber and thepoint where said second conductor is connected to said chamber, saidprojection being adjustable around the length of said chamber so that aportion of said projection is in the region of said first conductor oralternatively that none of said projection is in the region of saidfirst conductor.

9. in combination, an outer cylinder of electrically conductingmaterial, an inner cylinder of electrically conducting material, saidinner cylinder being located inside said outer cylinder and said innercylinder having a diameter substantially less than the diameter of saidouter cylinder so that said inner cylinder and said outer cylinder formwalls of a hollow cylindrical chamber located th re'oetween, a top platefilling the region between said inner cylinder and said outer cylinderat one end of said cylinders, a bottom plate filling the region betweensaid inner cylinder and said outer cylinder at the other end of saidcylinder so as to form, in conjunction with said inner cylinder, saidouter cylinder and said top plate, a cavity of rectangular cross sectionand extending in a closed loop, a first conductor for electromagneticoscillations connected to said cavity at a first point, a

ond conductor connected to said cavity at a second point around thelength of said cavity and a third conductor connected to said cavity ata third point around the length of said cavity, the distance betweensaid first conductor and said second conductor being equal to thedistance between said first conductor and said third conductor, a ridgedmember extending into said cavity so as to form, in conjunction with thewalls of said cavity a ridged waveguide over part of the length of saidcavity, said ridged member extending from the region of said secondconductor past said first conductor to the region of said thirdconductor, said ridged member being discontinuous over a portion of thedistance between said second conductor and said third conductor over theclosest path between said first conductor and said third conductor.

References Cited in the file of this patent UNITED STATES PATENTS2,412,159 Leeds Dec. 3, 1946 2,423,396 Linder July 1, 1947 2,514,957Larson July 11, 1950 2,520,220 Nergaard Aug. 29, 1950 2,567,748 WhiteSept. 11, 1951 2,573,713 Kannenberg Nov. 6, 1951 2,615,958 Phillips Oct.28, 1952 2,639,325 Lewis May 19, 1953 OTHER REFERENCES Tunable WaveguideFilters, by Sichol: et al., Proceedings of the I. R. E., vol. 39, issue9, pages 1055-1059, pub. September 1951.

